Telemeter



W. BAUERSFELD.

TELEMETER.

APPLICATION mfp ocT. s. 1914.

1,347,571, Patented July-27, 1920.

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W. BAUERSFELD.

` TELEMETER.l APPLICATION'HLED cT. e. |914.

Patented July 27, 1920.

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'WALTHER BAUERSFELD, 0F JENA, GERMANY, ASSIGNOR TO THE FIRM OF CARL ZEISS, OF JENA, GERMANY.

TELEMETER.

Specification of Letters Patent.

Patented July 27,1920.

.Applicationv led October 6, 1914. Serial No. 865,406.

ever, that, on passing from one position to the other, the relative loca-tion of the two images of an innitely distant object presented to the observer does not change independently of the relative position of those members of the lreflecting system, which are fixed together. Of this type of telemeter only one single kind'has up to-the present become known, viz. the one dealt with in the Patent Specification 1,085,883. In this kind of telemeter a reflecting system-belonging to the front part of the telemeter can be brought into two different locations; in both locations its error of refieXion is the same, both as regards its absolute value and its sign, consequently the telemeter as a whole has the property alluded to, that the relative location of the two images presentedto the observer is not altered by an interchange of the two positions, which `the members of the entire reflecting system g(viz. the movable reflecting system on the one hand and the fixed reflectors on the other hand) can occupy relatively to one another. The two base-lines belonging to a telemeter of Athis kind are the base-line proper, which is used when taking a range, and a second one, which is used when theinstrument is being adjusted and with which the two entering Vaxial rays have the distance zero from one anotherV in the plane of triangulation, z'. e. a base-line, which also has the value zero. Asis known from the Patent Specification 1,085,883, it is possible to adjust such a telemeterfwith the aid of an object at any desired distance without additional auxiliary means.. i

The telemeter according to the present invention differs from the telemeters just mentioned by havingrv both its baselines different from zero. lVhile the new telemeter is just as simply adjustable as the telemeters according to Patent 1,085,883, it can be fitted with such simple reflecting systems as are only possible with the other telemeters,

.when forms are employed, which are hardly suitable for being carried out in practice.

lith the telemeters having the base-line within the instrument the measurement rests, as is well known, on the principle, that the range is proportional to the product derived from the length `of the base-line and the` reciprocal of the value of the angle formed at the object, vthe range of which is tobe found, by the rays coming from the'said object to the ends of the base-line. Hence, when the telemeter has been adjusted, a single reading will suice, Jfor finding the size of the said angle and by that means the required range. When there are doubts as to the state of adjustment .of the telemeter,

with the telemeters not corresponding to Patent 1,085,883 an auxiliary measurement is carried out for an object having a known distance (c. g. an infinitely great one), with the telemeters accordingto Patent 1,085,883, for an object of unknown distance, the instrument, however, being temporarily given a base-line having the value zero.

In the new telemeter an object having an unknown distance is used, just as in the case of the telemeter according to Patent 1,085,883, for adjusting, however', a double measurement of the following kind is made with the two base-lines belonging to the telemeter. In the first place an auxiliary measurement is made for an object having any distance, this measurement being based on one of the base-lines, and with the aid lrays form with one another, which are directed toward the ends of aA base-line equal to the difference of the two base-lines of the telemeter. From this angle the distance of the obj ect employedmay be derived in any suitable manner, the value of the base-liney being based on the difference between the two base-lines used. Should it be desired to avoid specially deriving vthe range from the angle, a scale may be employed when measuring the Yangle, which, lilre the usual scales of telemeters, indicates ranges directly. Then that scale of the telemeter is used, which is intendedV :tor the measurements proper, its readings apply equally to the double measurements serving for the adj ustment, it these readings be multiplied by the quotient from. the difference between the two base-lines belonging to the telemeter and the length of the base-line on which thescale is based. lnV principle nothing would stand in the way ot itting the telemeter witha single range-scale only, which is Vbased on the diierence between the two base-lines, and employing the method of adjustment described, which after all gives the true range of the object employed.v For the purpose oi' reducing the time taken over the single measurements, however,l it will be found generally of advantage to carry out such an adjustment measurement with the aid of both base-lines only jfrom time to time, as a rule, however, to useonly one of the two base-lines for measuring.` rllhe true rnge of any suitable Vobject maythen be from time to time ascertained by a double measurement of the kinddescribed and the scale intended vfor the measurementsproper correspondingly corrected. Y

This method of ad'ustment corresponds to that described briefly yin theBritish Pat-V ent 5,267H ofV the year 19011 (p. 4, l; 23 to l.

35), The telemeter, however, for which the adoption of this Vmethod is there recommended, diilers substantially from Vthe present one. The telemeter there described consists of a prism eld-glass provided Vwith a measuring device and in front of which there is placed a reiecting system, the object of whichV is to increase the relative distance of the entrance axes of the telemeter with regardrto thatv of the entrance axes of The second base-line (in the above meaning ot the term) results, when the Vfield-glass is used by itself.

Hence, the unavoidable variations in the deiection oit the rays, etl'ected Vby the said, re-

`fleeting system, do not make their iniiuence felt with both measurements to beun- -dertaken for the adjustment of the telemet'er, while it is -justthe condition 'for anad-V justment, which is independent of such variations, that thevariations of the kind de scribed act-on both measurements, and in the same sense too. Y

AsA the adjustment'of the new telemeter is based, as explained above, on the Vdiier- 4Vrac'y increases, the greater the said differ-V ence between the two base-lines, its accuwhich is greater than one of the two baselines themselves, will obviously result, when Yene of the base-lines is given a value, the

sign et which is opposite to that of the other base-line.' This may be taken as re-y proper. ymended VYin certain cases to carry out a alized, when the ray pencilentering the instrument in the one case to the right of the observer enters in the other case to his left Vhand and vice versa.

.measurements, Vwhen the two base-lines diiier from one another in their absolute value. Y

As the double measurement serving for the adjustment 1s based on the difference be-V tweenV the two base-lines, its accuracy, when the two base-lines have .different signs, is greater. than that `of the measurements Hence, itV may be even recomdouble measurement of the kind described in place of one of the measurements proper, for instance on any occasion whenrit hapaccuracy of measurement.

In the Vannexed drawing Figure Vl is a diagrammatic plane view of the optical systemot atelemeter according tothe invention. Figs. Zand 3 show another such system in its measuring disposition and in its auxiliary measuring disposition serving for adjustmentrespectively. Figs. 4 to 7 show athird system, Figs. 4 and 6 being plan views. and Figs. 5 and 7` cross-sections on lines 5--5y and l1-770i Figs. 4 and 6 respectively. Figs. 4 and 5 represent one disposition andFigs. 6 and 7 the other disposition. Figs. 8 to ll'show a fourth system, Figs. 8 and l0 being front elevations, while Figs, 9 and 11 are plan views. Figs. 8 and 9 represent one disposition and Figs. l0 and ll the other disposition.

In the optical system of Fig. 1 in front of either of two objectives a is a pentagonal vprism Z). VA separating prism system of a direction of the axial ray passing'throughv itand which represents the adjusting de- Y vice of the telemeter.V A similarlyV displaceable glass wedge e2 behind-the right-hand objective indicates the measuring` device.

Vpens to be desirable to obtain anin'creasedA Y When the measurements proper are beingY made, the pentagonalV prisms are in the position shown in full lines. Should Vit be desired for adjusting the telemeter to carry out the double measurementV describedKV into the position indicated in full lines and with this positionthe second measurement is made. f

In Figs. 2 and 3 the optical parts are the same as in the example according to Fig. 1. For the auxiliary measurement, however, the right-hand objective prism, b2, in this case remains in its position, while the leiiti hand one, b1, is removed fromV the left-hand end of the instrument and is placed after being rotated through 180O in the plane of its principal section, before the right-hand end. lllhile in the former measuring position the direction of the base-line is, as usual, perpendicular to the direction of inspection into the instrument, in the latter position it is parallel to the same; hence,

the whole instrument must be rotated, when changing from one position to the other, through 90o.

In the next example, Figs. 4 to 7, the two base-lines are opposed to one another as regards their sign inv the above explained sense, while they agree as to their absolute size. The optical parts are again the same as in the example according to Fig. l, the entrance axis of the' left-hand pentagonal prism, 51, being, however, oppositely directed to that of the right-hand pentagonal prism, b2. In order to give both sides of the telemeter the same direction of outlook, in

' the position according to Figs. 4 and 5 a central reflector 50 is disposed in front of the right-hand pentagonal prism. In the position according to Figs. 6 and 7 the same central rei-lector is placed in front of theother pentagonal prism. While in the position according to Figs. 4 and 5 the direction of inspection of the instrument agrees with its direction of outlook, they are oppositely directed in the position according to Figs. 6 and 't'. Hence, when using this system, the former position will generally be used for the measurements proper and the latter position for the auxiliary measurement. On passing from one position to the other, the whole instrument must be rotated in the plane of triangulation through 180.

In the last example, Figs. S to ll, the sign of the base-line in the first position is opposite to that of the base-line in the second position, in their absolute size, however, the base-lines of the two positions agree. IV ith the position as in Figs. 8 and 9 a penta gonal prism again lies in front of each objective, both, however, with their surface of emergence turned away from the adjacent objective, the left-hand prism, b1, being displaced downward and the righthand one, 52, upward with respect to the objectives. The separating prism system 01,'

02, the ocular d1, Z2 and the wedges el and c2 again correspond to the same parts of the former examples. Two central reflectors f1 and f2 serve for transmitting the rays emerging from the left-hand pentagonal prism to the left-hand objective vand those emerging from the right-hand pentagonal prism to the right-hand objective. The position according to Figs. 10 and 'l1 is ob'- tained from this position by both pentagonal prisms being rotated in the plane of their principal section through 90, the lefthand one, b1, in the clockwise and the righthan'd one, b2, in the opposite direction; in

addition to this the left-hand prism is displaced upward and the right-handy one downward beyond the objectives. lThe rays .emerging lrom the left-hand pentagonal prism, b1, now enter at the right-hand end -of the telemeter the central reflector f2 and The adjustment of a telemeter according to the invention shall be explained with the aid of the last example. In the position according to Figs. 10 and 1l by displacing the measuring wedge e2 the indication infinity is set on a range-scale and for any object coincidence of the two measuring images is obtained by displacing the adjusting wedge e1. Thereupon, by rotating and displacing the objective prisms the system is brought into .the condition according to Figs. 8 and 9 and by the displacement of the measuring wedge e2 the coincidence of the measuring images, which was lost by the rearrangement of the parts, is reestablished for the same object. The reading on the said scale now gives the true distance of said object. By displacing the measuring wedge this reading is established on a second range-scale, the graduations of which have half the relative distance of those of the first scale and the thus lost coincidence of the measuring images restablished by displacing the adjusting wedge. The telemeter is now adjusted.

I claim:

l. In a telemeter containing two baselines differing from zero an objective system, a reflecting system, the members of which are adapted to be brought into two different relative positions, each base-line belonging to one such position of the said members, the relative location of the two images of an infinitely distant object presented to the observer by the telemeter remaining unaltered, on passing from the use of one base-line to the use of the other baseline, independently of the relative position of those members of the reiecting system, which are Yfixed together, and range-indicating means.V

2. In a telemeter containing two baselines differing from zero an objective system, a reflectingv system, the :members of which are adapted tobe brought into two different relative positions, each base-line belonging to onesuch position of the, said Vmembers, the relative location of the two images of an infinitely distant object presented tothe observer by thetelemeter remaining unaltered, on passing from the use of one base-line to the use of the other base line, independently` of the relative position of those members of the refiectingsystem,

' position of the said members, the relative location of the two images of an infinitely distant object presentedV to the observer by the telemeter 4remaining unaltered, on passing from the use of onebase-line to the use of the other base-line, independently of the relative position of those members ofthe reflecting system, which are fixed together,

y and range-indicating means. i Y

4. In 'a telemeter containing two baselines differing from zero and agreeing as to Y theirabsolute value, twoobjectives, an objective reflecting system located at either end of the telemeter and consisting of an optical square and of a central reflector, each optical square, when used in connection withone of the base-lines,` being adapted to transmit, together with the central reflector lying at the same end of the telemeter, and, when used in'connection with the other baseline, being adapted to transmit, together with the central reflector lying at the other end of thertelemeter, the rays entering the optical square to that. objective, which lies atfthe same end as the centralreflector, the relative location of the two images of an infinitely distant object presented t0V the obl server by the telemeter remaining unaltered,

on passing from the useV of one base-line to the use of the other base-line, independently of any variation of the angle of deflection of either optical square or of either central reflector, and rangeindicating means.

WALTIIER BUERSFELD. Witnesses y PAUL KRGER,

RICHARD HAHN. I, 

